1. Field of the Invention
This invention relates to methods and principles for apparatus for the manufacture of dairy products, from dairy starter cultures. Additionally, this invention relates to dairy products prepared by means of the disclosed method and apparatus and the use of the method and apparatus for manufacturing of dairy products.
2. Background
The preparation of most dairy products involves as a rule the use of microorganisms, in particular bacteria, such as e.g. lactic acid bacteria. Lactic acid bacteria are essential in the making of all fermented milk products, cheese and butter, and they are normally supplied to the dairy industry either as frozen or freeze-dried cultures for bulk starter propagation or as so-called “Direct Vat Set” (DVS) cultures, intended for direct inoculation to a fermentation vat for the dairy product.
In a commercial cheese production plant used at the present time, the time interval between successive inoculation of the culture into the cheese vats can typically vary from around 30 to 40 minutes in a large cheese plant with a vat size of around 26,000 liters, to only 1 to 2minutes in soft cheese production, using cheese vats of only around 200–300 liters in size.
A disadvantage by the use of pellets of frozen or freeze-dried DVS cultures, particularly with said small vat sizes, is that it requires a high degree of manual handling since the DVS culture has to be weighted out manually and then added separately to each cheese vat. Furthermore, because of a need for rapid filling and inoculation, particularly in soft cheese production, the manual addition of solid DVS cultures often presents a significant organisational and coordinational challenge regarding the planning of the working schedule for the staff, which eventually results in higher production costs.
WO-A-99/09838 describes a starter delivery system for direct and automatic dosage of DVS cultures in which the DVS culture is suspended in a water solution making a stable liquid culture suspension ready for direct inoculation into the cheese vat. However, although a stabilisation of the culture to be added is achieved the lag phase prior to growth is still unaltered and undesirably long.
In the production of different cheese types and fermented products there is a continuous need for very active cultures, in order to shorten the lag phase for fermentation in the production process, and thereby minimise the capacity cost for equipment.
Traditionally, high volumes of bulk starter cultures, typically constituting addition of 2–6% of the starter culture, have traditionally been employed, particularly in the production of e.g. set yoghurt and various soft cheeses, in order to e.g. shorten the lag phase. This also has the secondary effect of lowering the pH value of the milk immediately. However, the consequence of using said high dosage of bulk starter in combination with the slightly longer lag phase of DVS cultures, is obviously that the DVS cultures need a longer residence time when replacing the bulk starter with DVS cultures in production of dairy products. This is a problem in some production processes, because the required amount of DVS cultures is high implying relatively high production costs.
It is known from the prior art that DVS cultures can be pre-activated by blending the DVS culture with a small volume of preheated milk in a vessel or tank, and by pre-activating the culture for 30–60 min before addition to the cheese vat or the fermentation vessel. The preactivation is normally enabled by means of a range of vessels containing 20–50 liters of milk in which the DVS culture is added and kept for 30–60 minutes. Following an initial short period of incubation, the milk is ready for further inoculation of the cheese vat or fermentation tank over a period of time of 15–60 minutes. Normally, such systems are batch-type systems that frequently render significant variation in the preactivation time between fills, which is a problem in the quality control work and the planning and management of the production work.
It appears from the above that there is a clear need in the market for a method and apparatus that diminish the inter batch quality variation of the products, shorten the production time for fermented dairy products, facilitate the planning and management of the production work and reduce the production costs.